In the next few days, a defunct, unoccupied Chinese space station, Tiangong-1 meaning 'heavenly palace' – shown in the vivid image below, is expected to reenter the atmosphere following the end of its operational life. Most of the craft should burn up. Owing to wide variations in atmospheric dynamics and the break-up process, among other factors, the date, time and geographic footprint of the reentry can only be forecast with large uncertainties. In the history of spaceflight, no casualties from falling space debris have ever been confirmed.

Based on the geometry of the orbit, the ESA can exclude the possibility that any fragments will fall over any spot further north than its projected landing spans a region from 43˚N to 43˚S S latitude, a sizable percentage of the inhabited globe. Impact is more likely closer to the edges of that region, which includes nearly every major city in the United States.

The image above shows Tiangong-1, and was captured by French astrophotographer Alain Figer on 27 November 2017. It was taken from a ski area in the Hautes-Alpes region of southeast France as the station passed overhead near dusk. The station is seen at lower right as a white streak, resulting from the exposure of several seconds, just above the summit of the snowy peak of Eyssina (2837 m altitude).

As the ESA writes in an FAQ: “the personal probability of being hit by a piece of debris from the Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning." Additionally, this debris will be relatively small compared to other uncontrolled reentries.

A 13-agency consortium including NASA and others, called the Inter-Agency Space Debris Coordination Committee, has been monitoring the craft’s reentry, while the European Agency posts updates. As of now, the estimated impact window is between March 30 and April 2. "This means that reentry may take place over any spot on Earth between these latitudes, which includes several European countries. The date, time and geographic footprint can only be predicted with large uncertainties. Even shortly before reentry, only a very large time and geographical window can be estimated.

Tiangong-1 is 12 m long with a diameter of 3.3 m and had a launch mass of 8506 kg. It has been unoccupied since 2013 and there has been no contact with it since 2016. The station's mass and construction materials mean there is a possibility that some portions of it will survive and reach the ground.

The 13 space agencies/organisations of IADC are using this event to conduct their annual reentry test campaign, during which participants will pool their predictions of the time window, as well as their respective tracking datasets obtained from radar and other sources. The aim is to cross-verify, cross-analyse and improve the prediction accuracy for all members.